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Image Processing For BugGuide

Recently I gave some comments on a particular image and Beatriz requested a more permanent location for those comments. I thought this would be a good place to get feedback....

Here are a few suggestions on how contributors may want to process their images before uploading to BugGuide. These suggestions may help improve an image’s overall appearance, may help receive a more specific identification, and may help avoid unnecessary Frassing of otherwise valuable images.

For several reasons, cropping your images may be a necessity of life (at least here at BugGuide) :-) Here is just one example why Click here for an explanation
Cropping an image should NOT hurt the image quality (unless your software is really bad or something). The only type of crop that may have any visible effect on image quality is a diagonal or rotational crop (where the crop box is spun before cropping). Cropping an image is just selecting what part of the image you would like to discard vs. what part you would like to keep. Again, cropping should not harm the part you keep.

My method of cropping for BugGuide (you don’t have to do it this way)
First I use IrfanView to draw a crop-box around the bug, just the bug, from the tip of the antennae to the tip of the wing to tip of the foot, just the bug. Then I look at the size. Are all sides less than 560? If yes do process 1 else do process 2.
1) I increase the size of the crop-box to give a reasonable border around the bug without going over 560 on any side. Use your favorite software to crop it there.
2) I now know that the image will have to be resized down to 560x560, either by me and my software or by BugGuide and its software. So I again increase the borders of the crop-box this time giving only a relatively small margin around the bug, because that reduces the amount the bug needs to be shrunk. Use your favorite software to crop it there. But now you have to decide if you trust BugGuide to shrink you image or do you trust your software more? I like the control so I do my own resizing. Also, only you and the editors can see images larger than 560x560, so you need to consider if it is worth the extra server resources to upload some 3000x3000 image that no user can ever see? (I’m sure some people do it). I resize my image then upload. If there is some special feature of the bug which is needed for an ID, I crop that out separately and upload it as a second image. That way everyone can see the important detail (including experts who are not always editors), and it may help me get an ID, and it may also help others ID their bug in the future.

Resizing an image, either by you or by BugGuide, WILL hurt image quality (how much is determined by the software used and the amount). If an image is already lacking clarity and fine detail then viewing it at full size will show those flaws, but the image can be made to appear sharper by shrinking it to hide the degree of imperfection. But you are not increasing the amount of image detail, you are only making the imperfections less visible by shrinking the entire image. You will eventually lose image detail doing this type of “sharpening”.

Resizing an image UP WILL almost always make it look bad. Taking a 300x300 image and increasing it to 560x560 will probably make it look horrible and use extra server disk space.

Some people notice that when they crop an image it gets even worse looking or blurry. As mentioned above, resizing a blurry image down may help it appear sharper. You are probably unknowingly using this technique by sometimes leaving a big border around your image and the letting BugGuide shrink your image to 560x560. You don’t need to do that, just use your image processing software to resize the cropped bug DOWN until it appears sharp. But remember don’t shrink it so much you lose the detail needed to get an ID!

Now that you have cropped and resized the image to create the best possible end result, the final step that has an effect on your image quality is saving. When you save an image you will probably be offered an option of image quality vs. file size. Whether that option comes in the form of “small, medium, or large” or “1-12” you will have to decide how big a file is necessary to achieve the desired result. Play with it a little and see how low you can go and still have your image look great!

Note 1: I don’t use IrfanView for any real image processing, I just like the way their crop-box gives a running display of pixel size on the window title.

Note 2: Before cropping an image you may want to configure your image software to display at a fixed size, 50%, 75%, 100%. If you have your software set to “fit to screen” or “fill window” and you crop your image, the software will resize the remaining image to continue filling the screen. This may falsely make it appear as though you have lost image quality. This is NOT the case. Your software has just visually increased the size of the bug making it appear as though you have resized it UP.

Beatriz – I hope this is what you had in mind!

Open for comments and corrections…(I’m sure some real photographers can point out the mistakes, really please do)

I thought I'd comment because of all the discussion about lossless crop. It's an interesting and useful discussion, but I want to make sure that people don't overlook one of the important points of John Maxwell's original post.

Sometimes a user will say that, when he crops an image, it gets all grainy. Ninety-nine percent of the time, he's talking about the graininess that results from automatically zooming in to make the crop fill as much screen space as the original image. Lossless crop would not be a solution for these users. They just need to understand that the graininess is not a result of cropping, but a result of zooming in, and not something they should try to avoid by not cropping. (See John Maxwell's note 2 above)

Lossless cropping.
It's possible to crop a JPEG losslessly, that is, without having to recompress the newly cropped image. This is the way to go if you really don't want to lose image quality. There's a list of software based on jpegtran here, but it's not always clear from the description if lossless cropping is supported. For Linux users, CropGUI works well. Don't personally know about other platforms.

I'm able to open JPEGs with just Microsoft Word.
via right mouse selection. Cropping therein I believe is "lossless" in my limited editing experience doing image edits.

It's unlikely...
that Word would implement lossless crop; it's not even that common in dedicated image editing software, as far as I know. The reasons being that it has limitations - primarily that the crop boundaries can only be moved in increments of 8 (or possibly 16, depending on how the image was originally compressed) pixels. It's hard to implement an interface for this that won't confuse users, so it's kind of a specialist thing, as argued about here... although that discussion implies that the feature was added to IrfanView at some point, so that might be the best bet for a free solution for Windows users.

The only reason I mention it here is that bug photos might well be a case where you want to retain as much image quality as possible from the original, being that you're effectively losing resolution already just by cropping, and fine details are likely to be more important than they are in, say, a picture of someone's cat. :)

Lossless JPEG Crop Common Now
Many free editors (Irfanview, Faststone) now use losseless crop and lossless preset rotations - there is no limit with "increments of 8". Can't speak for Windows Live Photo Gallery, Office Suite or Mac. Junkyardsparkle linked to a discussion from 2007 - ancient history in computer technology :)

However, as soon as one does ANYTHING else (free rotation, straighten, color tweaking, levels, curves, resizing (up or down) which is not the same as cropping, or even opening the image again it becomes lossy and details will be compromized.

Of course, the finest details continue to come from RAW images even though JPEG engines have improved remarkably in the last few years.

I hope you don't mind, but I went back in to my article, BugGuide Photography For The Beginner, and linked back to this article, from where I spoke about cropping. I think this would be a useful thing to know for anyone who happens to end up over there.

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